(a) Technical Field
The present invention relates to a canned motor for reducing a cogging torque. More particularly, it relates to a canned motor for restraining a cogging torque from being generated by inserting magnetic metal pins into slot openings of a stator, thereby reducing noise and vibrations during the operation of the canned motor.
(b) Background Art
A canned pump is generally used to increase a hydraulic pressure, e.g., a pump motor. The canned pump is configured so that a coil of a motor, i.e., a power source of the pump, is sealed by a “can” enclosure and the water compressed by the pump reciprocates between a rotary shaft and a rotor received within the can so that the water that is cooling the frictional heat generated by a rotating body in an appropriate way can act as a lubricant around the rotational friction part. A canned pump is generally manufactured by integrating an impeller and a motor. That is, a canned motor, i.e., a power source of a canned pump, is generally integrally coupled to the canned motor so as to prevent leakage of liquid.
Referring to FIG. 1, a conventional canned motor includes a housing 1 having a certain volume, a stator 2 installed on an inner peripheral surface of the housing 1, a coil (not shown) installed at a periphery of the stator 2 to create an electromagnetic interaction between the stator 2 and a rotor 3, a can 4 inserted into the housing 1 so as to seal the coil and the stator 2, a rotor 3 received and rotatably installed within the can by an electromagnetic interaction, and a rotary shaft 5 press-fitted with the rotor 3 to be rotated in conjunction with the rotor 3.
An impeller 6 of a pump is coupled to one end of the rotary shaft 5, and as the rotor 3 is rotated, the impeller 6 is rotated in conjunction with the rotary shaft 5 to suck and discharge water. The can 4 serves to prevent water from being leaked to the outside of the can 4 within which a coil is installed, and is generally made of polyphenylene sulfide (PPS).
As illustrated in FIG. 2, the stator 2 is installed on an outer peripheral surface of the can 4. If an electric power is applied to the coil, the stator 2 rotates and drives the rotor 3 due to an electromagnetic interaction with the rotor 3. A plurality of slots 7 are circumferentially formed in the stator 2, and slot openings 8 having a size of approximately 0.8 mm are formed between the slots 7 and the can 4. Although the conventional canned motor has a simple structure and excellent waterproofing performance, a high cogging torque is generated due to the slot openings of the stator, severely causing noise and vibrations.